Change label on form from thread

[FrankZA]

Hi

I am busy writing a program that is supposed to evaluate some algorithms (by time or result). When the program loads, a form appears. Once some selections in comboboxes have been made, the "Start" button begins the process.

I have used threads so that I can change the priority. Result evaluation can be run on a "belownormal" priority, while the time evaluation would be better when running on "highest" priority so that anything else that Windows is running has a lesser effect (or am I wrong here).

My code has the following structure:

Public Class Form1

  Private Sub Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button.Click

    Dim C1 as New Class1
    Call C1.NotCompare()
    C1 = Nothing

  End Sub

End Class


Public Class Class1

  Public Sub NotCompare()

    Dim t As Threading.Thread
    t = New Threading.Thread(AddressOf Me.Compare)
    t.Priority = ThreadPriority.AboveNormal
    t.Start()
    Thread.Sleep(0)

  End Sub

  Public Sub Compare()

    Dim i as Integer
    For i = 0 to AlgorithmList.GetUpperBound(0)
      Form1.AlgorithmLabel.Text = AlgorithmList(i).Name 'This is where the problem lies I think
    Next
    i = Nothing

  End Sub

End Class

I am attempting to to write the name of the algorithm to the label AlgorithmLabel on the original form Form1. I also want to write the name of the dataset in use to the form so that the user knows how far along the calculations the thread is (I assume this would be done in the same way).

How would I approach this problem of changing the label's text from a thread? Or is there a better approach?

Also, is it useful to use the Sleep(0) option at all?

Thanks...

[zdavis]

If I have understood the question correctly

I would declare an event in your thread and then subscribe to the event from your main form.
Depending on what you want to whether you need your own event args class you could do something like

//Thread event
public static event EventHandler yourEventName;

subscribe to the event on your main form

classname.yourEventName += mainform_yourEventName;

after you have that done you should be able to use the following class to invoke the event across threads.

public static class Invoker
    {
        public static void Invoke(Delegate delegateToCall, params object[] argsOfDelegateToCall)
        {
            foreach (Delegate del in delegateToCall.GetInvocationList())
            {
                ISynchronizeInvoke si = del.Target as ISynchronizeInvoke;
                if (si != null && si.InvokeRequired)
                    si.Invoke(del, argsOfDelegateToCall);
                else
                    del.DynamicInvoke(argsOfDelegateToCall);
            }
        }
    }

Invoke the event

invoker.invoke(myHandler, this, eventargs.empty);

Hopefully that helps

-zd

[zdavis]

Sorry....I just realized that this is the VB forum....Sorry for the confusion.

[FrankZA]

Sorry....I just realized that this is the VB forum....Sorry for the confusion.

Would something like this work in VB? I have no experience in other languages, but I would guess that was some form of C.

[zdavis]

Yeah....That was in C#. I will try to convert that over to vb today and repost.

[FrankZA]

Thanks zd, I would appreciate that a lot!